Thermal interface materials and methods for their preparation and use

Abstract

A curable composition contains (A) a polyorganosiloxane base polymer having an average per molecule of at least two aliphatically unsaturated organic groups, optionally (B) a crosslinker having an average per molecule of at least two silicon bonded hydrogen atoms, (C) a catalyst, (D) a thermally conductive filler, and (E) an organic plasticizer. The composition can cure to form a thermally conductive silicone gel or rubber. The thermally conductive silicone rubber is useful as a thermal interface material, in both TIM1 and TIM2 applications. The curable composition may be wet dispensed and then cured in situ in an (opto)electronic device, or the curable composition may be cured to form a pad with or without a support before installation in an (opto)electronic device.

The invention claimed is: 
     
       1. A method comprising:
 1) curing a composition comprising:
 (A) a polyorganosiloxane base polymer having an average per molecule of at least two aliphatically unsaturated organic groups, 
 optionally (B) a crosslinker having an average per molecule of at least two silicon bonded hydrogen atoms, 
 (C) a catalyst selected from hydrosilylation reaction catalyst and peroxide cure catalysts, 
 (D) a thermally conductive filler, and 
 (E) an organic plasticizer soluble in ingredient (A), which does not inhibit curing of the composition, thereby preparing a cured silicone, and thereafter 
 2) interposing the composition of step 1) along a thermal path between a heat source and a heat dissipator. 
 
 
     
     
       2. The method of  claim 1 , where ingredient (D) comprises: aluminum nitride, aluminum oxide, aluminum trihydrate, barium titanate, beryllium oxide, boron nitride, carbon fibers, diamond, graphite, magnesium hydroxide, magnesium oxide, metal particulate, onyx, silicon carbide, tungsten carbide, zinc oxide, and a combination thereof. 
     
     
       3. The method of  claim 1 , where ingredient (E) has an average, per molecule, of at least one group of formula 
       
         
           
           
               
               
           
         
       
       where R represents a hydrogen atom or a monovalent organic group. 
     
     
       4. The method of  claim 1 , where ingredient (E) has a formula: 
       
         
           
           
               
               
           
         
       
       where X represents a cyclic hydrocarbon group, subscript x has a value ranging from 3 to 15, each R 1  is independently a branched or linear monovalent hydrocarbon group, and each R″ is independently a branched or linear hydrocarbon atom or a monovalent organic group. 
     
     
       5. The method of  claim 1 , where ingredient (E) is selected from the group consisting of bis(2-ethylhexyl) terephthalate; bis(2-ethylhexyl)-1,4-benzenedicarboxylate; 2-ethylhexyl methyl-1,4-benzenedicarboxylate; 1,2cyclohexanedicarboxylic acid, dinonyl ester, branched and linear; bis(2-propylheptyl) phthalate or di-(2-propyl heptyl) phthalate; diisononyl adipate; trioctyl trimellitate; triethylene glycol bis(2-ethylhexanoate); diethylene glycol dibenzoate; 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane; di(2-ethylhexyl) phthalate; bis(2-ethylhexyl) adipate; dimethyl phthalate; diethyl phthalate; dibutyl phthalate; di-2-ethylhexyladipate; 1,2, 4-benzenetricarboxylic acid, tris(2-ethylhexyl) ester; trioctyl trimellitate; triethylene glycol bis(2-ethylhexanoate); bis(2-ethylhexyl) terephthalate; diethylene glycol dibenzoate; 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane; 1,2,3-triacetoxypropane; a fatty acid ester; and a combination thereof. 
     
     
       6. The method of  claim 1 , further comprising: an additional ingredient selected from (F) a spacer, (G) a reinforcing or extending filler, (H) filler treating agent, (I) an adhesion promoter, (J) a vehicle, (K) a surfactant, (L) a flux agent, (M) an acid acceptor, (N) a stabilizer, and a combination thereof. 
     
     
       7. The method of  claim 1 , further comprising: applying the composition to a support before step 1). 
     
     
       8. The method of  claim 1 , where the heat source comprises an (opto)electronic component. 
     
     
       9. The method of  claim 1 , where the heat dissipator comprises a heat sink, a thermally conductive plate, a thermally conductive cover, a fan, or a circulating coolant system. 
     
     
       10. An interface material comprising:
 0) a support, and 
 I) a cured silicone prepared by curing a composition comprising:
 (A) a polyorganosiloxane base polymer having an average per molecule of at least two aliphatically unsaturated organic groups, 
 optionally (B) a crosslinker having an average per molecule of at least two silicon bonded hydrogen atoms, 
 (C) a catalyst selected from hydrosilylation reaction catalyst and peroxide cure catalysts, 
 (D) a thermally conductive filler, and 
 (E) an organic plasticizer soluble in ingredient (A), which does not inhibit curing of the composition, where the composition is coated on two sides of the support; and where the cured silicone is formed as a flat member, a 
 
 hemispherical nubbin, a convex member, a pyramid, or a cone. 
 
     
     
       11. The interface material of  claim 10 , where the support comprises a carbon fiber mesh, a metal foil, a perforated metal foil, a filled or unfilled plastic film, or a woven or nonwoven substrate. 
     
     
       12. The interface material of  claim 10 , further comprising II) a release sheet covering a surface of the cured silicone opposite the support. 
     
     
       13. A device comprising:
 a) a heat source, 
 b) the interface material of  claim 10 , and 
 c) a heat dissipator; 
 
       where the thermal interface material is positioned between the heat source and the heat dissipator along a thermal path extending from a surface of the heat source to a surface of the heat dissipator. 
     
     
       14. The device of  claim 13 , where the heat source is an (opto)electronic component. 
     
     
       15. Use of the interface material of  claim 10 , in an application selected from the group consisting of TIM1, TIM2, or both.